The present invention relates to spray elastomers and a process for preparing these spray elastomers. In the process of the present invention, solid fillers are incorporated into each of the isocyanate and isocyanate-reactive components. This spraying process makes it possible to produce elastomers having higher solids contents than was previously possible. The elastomers produced by the process of the present invention are particularly useful as acoustic components for automotive applications such dashboard insulators and carpet backing.
The inclusion of solids in polyurethane elastomers makes it possible to reduce the cost of such elastomers without sacrificing physical properties of the elastomer. It is therefore commercially desirable to increase the solids content of polyurethane elastomers to the highest possible level.
The amount of solids cannot, however, be increased to a level so high that processing of the polyurethane-forming components becomes too difficult to be commercially viable.
U.S. Pat. No. 6,432,543 discloses a specific sprayable elastomer composition for making components which are particularly suitable for the automotive industry. These components have a molded elastomeric outer layer and an inner polyurethane foam layer. The elastomer is the reaction product of an aromatic polyisocyanate, a solids-containing polyol, a second polyol, and other additives. The total solids content of all components except the polyisocyanate is up to 40 wt. %. Hardness of elastomers containing this amount of solids is generally limited to the range of 70 to 85 Shore A. U.S. Pat. No. 6,432,543 does not, however, teach that the disclosed elastomers could have solids contents greater than 40%.
In currently available polyurethane spray elastomer systems, the solids are incorporated only in the isocyanate-reactive component as is taught in U.S. Pat. No. 6,432,543. Production of elastomers with high solids contents (i.e., solids contents greater than 40%) is, however, limited by this approach because the amount of solid material that can be incorporated into the isocyanate-reactive component cannot be so great that the viscosity of the isocyanate-reactive component is too high for spraying. To achieve higher solids contents, it is therefore necessary to adjust the volume ratio of the isocyanate component being combined with the solids-containing isocyanate-reactive component. The volume ratios (i.e., volume of isocyanate-reactive component to isocyanate component) currently being used in known spray polyurethane elastomer systems generally range from 11:1 to 14:1. Such volume ratios require the use of specialized equipment.
It would therefore be advantageous to develop a spray process for the production of polyurethane elastomers having a solids content greater than 40% that could be conducted using conventional spray equipment.